Fix empty-string fields on CaN not working (#2120)

temporal-test-server/src/main/java/io/temporal/internal/testservice/StateMachines.java

@@ -936,12 +936,12 @@ private static void continueAsNewWorkflow(
     } else {
       a.setWorkflowRunTimeout(sr.getWorkflowRunTimeout());
     }
-    if (d.hasTaskQueue()) {
+    if (d.hasTaskQueue() && !d.getTaskQueue().getName().isEmpty()) {
       a.setTaskQueue(d.getTaskQueue());
     } else {
       a.setTaskQueue(sr.getTaskQueue());
     }
-    if (d.hasWorkflowType()) {
+    if (d.hasWorkflowType() && !d.getWorkflowType().getName().isEmpty()) {
       a.setWorkflowType(d.getWorkflowType());
     } else {
       a.setWorkflowType(sr.getWorkflowType());

temporal-test-server/src/test/java/io/temporal/testserver/functional/ContinueAsNewTest.java

@@ -0,0 +1,118 @@
+/*
+ * Copyright (C) 2022 Temporal Technologies, Inc. All Rights Reserved.
+ *
+ * Copyright (C) 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this material except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.temporal.testserver.functional;
+
+import io.temporal.api.common.v1.WorkflowExecution;
+import io.temporal.client.WorkflowOptions;
+import io.temporal.client.WorkflowStub;
+import io.temporal.common.WorkflowExecutionHistory;
+import io.temporal.common.interceptors.*;
+import io.temporal.testing.internal.SDKTestWorkflowRule;
+import io.temporal.testserver.functional.common.TestWorkflows;
+import io.temporal.worker.WorkerFactoryOptions;
+import io.temporal.workflow.ContinueAsNewOptions;
+import io.temporal.workflow.Workflow;
+import java.time.Duration;
+import org.junit.Assert;
+import org.junit.Rule;
+import org.junit.Test;
+
+public class ContinueAsNewTest {
+
+  @Rule
+  public SDKTestWorkflowRule testWorkflowRule =
+      SDKTestWorkflowRule.newBuilder()
+          .setWorkerFactoryOptions(
+              WorkerFactoryOptions.newBuilder()
+                  .setWorkerInterceptors(new StripsTqFromCanInterceptor())
+                  .build())
+          .setWorkflowTypes(TestWorkflow.class)
+          .build();
+
+  @Test
+  public void repeatedFailure() {
+    WorkflowOptions options =
+        WorkflowOptions.newBuilder()
+            .setWorkflowTaskTimeout(Duration.ofSeconds(1))
+            .setTaskQueue(testWorkflowRule.getTaskQueue())
+            .build();
+
+    TestWorkflows.WorkflowTakesBool workflowStub =
+        testWorkflowRule
+            .getWorkflowClient()
+            .newWorkflowStub(TestWorkflows.WorkflowTakesBool.class, options);
+    workflowStub.execute(true);
+
+    WorkflowExecution execution = WorkflowStub.fromTyped(workflowStub).getExecution();
+    // Verify the latest history is from being CaN'd
+    WorkflowExecutionHistory lastHist =
+        testWorkflowRule.getExecutionHistory(execution.getWorkflowId());
+    Assert.assertFalse(
+        lastHist
+            .getEvents()
+            .get(0)
+            .getWorkflowExecutionStartedEventAttributes()
+            .getFirstExecutionRunId()
+            .isEmpty());
+  }
+
+  public static class TestWorkflow implements TestWorkflows.WorkflowTakesBool {
+    @Override
+    public void execute(boolean doContinue) {
+      if (doContinue) {
+        Workflow.continueAsNew(false);
+      }
+    }
+  }
+
+  // Verify that we can strip the TQ name and test server continues onto same TQ
+  private static class StripsTqFromCanInterceptor extends WorkerInterceptorBase {
+    @Override
+    public WorkflowInboundCallsInterceptor interceptWorkflow(WorkflowInboundCallsInterceptor next) {
+      return new WorkflowInboundCallsInterceptorBase(next) {
+        @Override
+        public void init(WorkflowOutboundCallsInterceptor outboundCalls) {
+          next.init(new StripsTqFromCanCmd(outboundCalls));
+        }
+      };
+    }
+  }
+
+  private static class StripsTqFromCanCmd extends WorkflowOutboundCallsInterceptorBase {
+
+    private final WorkflowOutboundCallsInterceptor next;
+
+    public StripsTqFromCanCmd(WorkflowOutboundCallsInterceptor next) {
+      super(next);
+      this.next = next;
+    }
+
+    @Override
+    public void continueAsNew(ContinueAsNewInput input) {
+      next.continueAsNew(
+          new ContinueAsNewInput(
+              input.getWorkflowType(),
+              ContinueAsNewOptions.newBuilder(input.getOptions()).setTaskQueue("").build(),
+              input.getArgs(),
+              input.getHeader()));
+    }
+  }
+}

temporal-test-server/src/test/java/io/temporal/testserver/functional/common/TestWorkflows.java

@@ -30,6 +30,12 @@ public interface PrimitiveWorkflow {
     void execute();
   }
 
+  @WorkflowInterface
+  public interface WorkflowTakesBool {
+    @WorkflowMethod
+    void execute(boolean arg);
+  }
+
   @WorkflowInterface
   public interface WorkflowReturnsString {
     @WorkflowMethod